Method of concentrating milk



July 8, 1952 G. cuNNxNGHAM 2,602,745

METHOD oF CONCENTRATING MILK Filed June 24, 1949 l0 ATTORNEYS l'The primary Patented July 8, 1952 PATENT` oFF-ICE f2 g VVVivlurrnon oF ooNoEN'TRA'rlNG MILK "vGeoi'ge iL. Cunningham, Cincinnati, Ohio', as-

signor to `The Commonwealth Company of Ohio; Dayton,

Engineering Ohio, a corporation Application 124, 1949', seria1N0. 101,236"

heretofore, none of these products could be made without-substantial changes inithe'flavor, texture, 'or' aroma which greatly detracted from the palatability of the'fproduct when restoredto 1 its original concentration by the addition of water. In general,` this change in taste, texture' and aroma, was due to chemical changes in thefmilk, ,or to the loss therefrom of volatile flavoring substances when heat or vacuum, or a combination of both, was applied to the milk to cause evaporation of water therefrom. So far as the applilcant knows', all present-day commercial processes for concentrating milk are characterized by removing water therefrom by evaporation, and, thus, all present-day commercial condensed, evaporated, or dried milk products are characteriz'ed by substantial and undesirable flavor changes. l Y

object of this invention'isto 'provideV a concentrated milk product and'a "method 'of making itcharacterized bythe vprodduct vlia-'ving'Ltliesame'` flavor as the original-milk ,-Anotherv'obje'ct isthe'provision of aniethod of y vconcentratin'g milk without the use of evaporating heiques,

we f gow made, maar Another object of my invention is to provide `'concentrated 'whole milk without breaking the emulsion, and Vwithout precipitating' the butterfat.

It is a further object, of my invention to provide'a concentratedmilk product havinga conjcentration of solids of 'not lessi thanYtwenty-six percent and preferably of approximately thirtyeight per cent.' l It is"also`an objectief the inventionto produce 'such a concentrate'of milk in either unfrozen or frozen form capable of being reconstituted rto initialconce'ntration by the addition of the sameamount of water that has been extracted,

andcharacterized by no change in taste from the original' milk.

f"-S2Still another object vofthe present invention `is to .provide such a'product which has nothing .except .water removed from it, so that its .origvin'al vitamin,mineral, and butterfat composition fisundisturbed.. I

Y"It anobject of my invention to provide 'such 'a reduction in volume of whole milk that it can -be supplied in'either 'unirozenv or frozen form,

Vin `such a relatively small packagel as` compared (Cl. 299-.-55) I 'with its original bulk as greatly lto reduce the oost of packaging, the cost of' distribution, and

the frequency of distribution to th'econsumer. 1t isla further object o f my invention tol'pro- Avide a whole milk concentrate which can easily be preserved over long periods without deterioration. v 'i 'i Y' It is a further object of the inventionA to -'provide such Aa product, and the process ofmaking it, so that the concentrated product may enter Ainto a subsequent process of making powdered milk or evaporated milk, eliminating from such "products the change in taste now so vobjectionable in dried milk and in evaporated milk. These and other objects and advantages will become more apparent upon 'reference to the following description taken in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic view showing one form of apparatus adapted for carrying out my invention;-` r A l Figure2 is a section on line Z-Zof Figure 1 showing theap'paratus in cross-section; and Y Figure`f3is'`a chartdiagrammatically illustrating the carryingout of a process according 'to' 'my linv'ention. Y

lThe substance to b e concentrated may be placed Ylinfa container I0, whence'it ows through pipe v',IQZfa'nd control fvalve I l intoa trough-like `element. I6, in which the jirst step of the process according to my invention'is carried out.

As mentionedpreviously,this invention is pri'- marily concerned with the concentration of milk, and this may be either'whole milkor' vskimmed Vmilk, according Atov the iinal product desired.

The trough-like element I (iis arrangedin cascade with two other similar elements I8 and 20,

so the miikfwhich enters the left side of eiementrlr 6 will overflow the right end thereof into velement I8, and then overflow the right vendfof element, I8 into element 20.A rlhe rightend'of element 2l!V is arranged to overflow into a cenvlltrifuge 2 2fand then to pass therefrom through conduit 24 into a'suitable receiving container v2li. According to this invention,'each of the troughlike elementsY I6, I8, and 20 has'asrsoeiated there- `with a screened barrienmember' 28; andA all of the'elenents 28fare interconnectedV by 'a parallel motion linkage, generally indicatedat 30, and by "means, ofwhichthev 'barrier Amembers can be moved in a circuitous path in the direction indicated by arrow 32.

The barrier members 28 are supported on crank arms 34 that are fastened to shafts 3B mounting bevel gears 38 that mesh with other bevel gears 4U on a drive shaft 42 drivingly connected with motor 44.'- It will be apparent that energization of motor 44 will cause rotation of crank arms 34 and movement of the screened barrier members 28 in a circuitous path clockwise.

Each of the trough-like elements I 6, I8, and is placed in a suitable container and refrigerant circulated thereabout. '.The .containers are indicated at 4S, 48, and 58, and each thereof` has inlet and outlet pipes, as indicated at 52.

The purpose of the refrigerant circulated through the above-mentioned containers isI to chill the milk within the trough-like elements until ice crystals form therein. It is a wellknown fact that the ice crystals formed when any aqueous solution, mixture, or emulsion is chilled to the freezing point are pure ice.

Ordinarily, and such is the case withA milk, the rice formation is .in the form of very tiny crystals, and as the milk freezes and these tiny crystals become multiplied, they hold in physical combination with them the other milk products, so` that, While frozen milk is characterized by the water being separated from the other parts of the milk in that it has been converted to pure ice crystals, it has been found impossible physicallyto extract the water. This isgdue to the fact that the very great surface of the tiny ice crystals in frozen milk retain enough of the other parts of the milk thereon as a surf Vcrystals can readily be removed from the milk and carry with them only a small amount of the milk, because their surface area is relatively l small as compared to their volume. y

Referring again to Figure l, the milk which isintroduced into trough-like element IB at the left side thereof is chilled within Ythe said'element to a temperatureA of about y-3 degrees centigrade. As the milk moves rightwardly toward element I6 toward itsL point of .overflow into element I S, icev crystals will commence to form therein. If these crystals are small enough to pass through barrier member 28, then they will overflow with Vthe milk into element I8. However, if the crystals are of such a size that they will be caught by barrier28, then they will be moved thereby toward the point of entry vof milk into element I8 and discharged from vthe said element to centrifuge .54.. Within centrifuge 54 the milk entrained with the ice crystalsfis separated therefrom and `flows through conduit 56 into chamber 58. andA is pumped therefrom by pump Gfthroughconduit to a lower'temperature than that in element I8 because the milk in element I8 isnow somewhat concentrated and a' lower temperature must be- 4 attained before ice crystals will form or grow therein. The actual temperature to which the milk is reduced in element I8 is about -15 degrees centigrade. Within element I8, the process continues with ice crystals forming and growing therein, and those which are small v.enough-to, passV through barrier'128 pass on to element 20, while those large enough to be caught by barrier member 28 are transferred back into element I8 to be caught by the barrier member 28therein andconveyed to centrifuge 54.

Within element 20, the milk, now fairly concentrated, is reduced to that temperature which willcause ice-crystals to form and grow, this temperature being in the neighborhood of 25 degrees centigrade. The same action takes place within element 20 as takes place vwithin elements I6 and I8, and a substantial amount of ice crystals is moved by barrier member 28 from element 2U into element I8, while some fine ice crystals will be discharged from the right side of element 20 into centrifuge 22. Y

It is to be-noted at this time that the ice is always moving in counterow relationship with the milk, and that the ice crystals are removed from the system at the point of entryl therein of the milk to be concentrated, This causes the lcrystals to be washed in the most dilute milk available in the system and reduces to a Vsubstantial degree the amount of carry out of milk by the crystals.

It is also to be noted that once the system has become Y stabilized, most of the initial crystal formation takes place in elements I8 and 20, with substantially all of the water taken from the milk in Velement ,I6 going to crystal growth and a substantial amount of the water taken from the milk in element I8 going for the same purpose.

It will be apparent that while I have shown and described a three-step process for concentrating. milk by freezing, as many steps Aas necessary-.couldbe employed, or the process could be carriedout as a continuous Icycle. The essentialxthing is .that the milk is moved in one Vdirection and subjected to progressivelydecreasing temperatures, while the ice formed inthe milk is moved in counterflow relationship therewith and-removed from the milk stream at the entry thereof into the system. Y f

Referring briefly to the drawings again, centrifuge 22 is adaptedforoperation by a motor 84, centrifuge 54 is adapted for operation by motor-68, and pump Buis adapted for operation by motor 68.

Figure 2is a cross-sectional View indicating how the barrier member 28 lextends from side to side of the trough-like element in which it is placed, so as to form an effective means for removing all ice crystals above a predetermined size from the milk streampassing through the saidgelement. v f

. In Figure 3 there is diagrammatically illustrated the carrying out of a process according to'this invention. In this figure, the solid line indicated at 'ID represents the part of'the milk which it is desired to retain Yin the product, while the dashed line at 'I2 indicates the 'water'it is desired to remove from the milk It will be seen in Figure 3 that the water and milk leave container I8 together and then pass along'a path 'which 'is continuously lower in' temperature.

-The water'represented by line I2 is gradually resented by the dotted line 14.

the water is reversed, and it then passes in counteriiow relationship with the milk, as rep- At the left end, the ice is centrifuged in centrifuge 54, and the milk removed therefrom is returned to the system, while at the right end, the milk product is centrifuged in centrifuge 22, and the icev removed therefrom and preferably returned to the system to effect a heat economy.

The concentrated product delivered to the container 26 may then be packaged for distribution in either a frozen or unfrozen state, or it may be passed through other processes in order to reduce it to a dried product or to further concentrate it for some particular purpose.

In any case, the advantage obtains that when the product is restored to its initial concentration by the addition of water, the flavor is unchanged. Due to the fact that the water is removed solely by a freezing process, the vitamins and the iiavor and aroma producing substances are not changed or removed from the milk. Also, since the milk is continuously kept in motion during its concentration' and the crystal growth therein is at a relatively slow rate, there is no breakdown of the emulsion and no precipitation or coagulation of the butterfat.

It will be understood that I do not wish to be limited to the exact proportions, ratios, and other factors specifically set forth in the foregoing description and the accompanying drawings but desire to comprehend such changes thereof as may be further desirable to adapt my invention to different conditions and usages.

I claim:

l. A method of treating liquid food stuffs to produce a concentrate thereof which comprises the steps of (a) flowing said liquid food stuff in the form of a cascade through a plurality of freezing treatment stages and whereby the liquid.

food stu being concentrated passes from one freezing treatment stage to another down the series, (b) subjecting said liquid food stuff in each stage to a freezing treatment and sufficient to cause the formation of ice crystals, (c) removing a portion of said ice crystals from each treatment stage as the liquid food stuff cascades down through the series of freezing treatment sultant liquid food stuff after passing through said cascade series of freezing treatments to remove the remaining ice crystals therefrom to produce a concentrated liquid food stuif.

3. A method of treating milk to produce a concentrate thereof which comprises the steps of (a) flowing said milk in the form of a cascade lthrough a plurality of freezing treatment stages and whereby the milk being concentrated passes from one freezing treatment stage to another down the series, (b) subjecting said milk in each stage to a freezing treatment and suicient to cause the formation of ice crystals, (c) removing a portion of said ice crystals from each treatment stage as the milk cascades down through the series of freezing treatment stages, (d) transferring the ice crystals removed from one treatstages, (d) transferring the ice crystals removedA from one treatment stage to the preceding `treatment stage, and (e) treating the resultant liquid food stuif after passing through said cascade series of freezing treatments to remove the remaining ice crystals therefrom to produce a concentrated liquid food stuff.

2. A method of treating liquid food stuffs to produce a concentrate thereof which comprises the steps of (a) flowing said liquid food stuff in the form of a cascade through a plurality of freezing treatment stages and whereby the liquid food stuff being concentrated passes from one freezing treatment stage to another down the series, (b) subjecting said liquid food stuff in each stage to a freezing treatment and su'icient to cause the formation of ice crystals, (c) removing a portion of said ice crystals from each treatment stage as the liquid food stuff cascades therealong down through the series of freezing treatment stages, (d) transferring the ice crystals removed from one stage of treatment to the next preceding treatment and in a direction counter to the cascading liquid food stuff, and (e) removing ice crystals from the initial stage treatment and centrifuging the same to remove liquid fend therefrom, and if) treating the rg- ,75, 5,375

ment stage to the preceding treatment stage, and (e) treating the resultant milk after passing through said cascade series of freezing treatments to remove the remaining ice crystals therefrom to produce a concentrated milk.

4. A method of treating milk to produce a concentrate thereof Which comprises the steps of (a) flowing said milk in the form of a cascade through a plurality of freezing treatment stages and whereby the milk being concentrated passes from one freezing treatment stage to another down the series, (b) subjecting said milk in each stage to a freezing treatment and sufficient to cause the formation of ice crystals, (c) removing a portion of said ice crystals from each treatment stage as the milk cascades therealong down through the series of freezing treatment stages, (d) transferring the ice crystals removed from one stage of treatment to the next preceding treatment and in a direction counter to the cascading milk and (e) removing ice crystals from the initial stage treatment and centrifuging the same to remove milk therefrom, and (f) treating the resultant milk after passing through said cascade series of freezing treatments to remove the remaining ice crystals therefrom to recover a concentrated milk.

`5. A method of treating milk to produce a concentrate thereof which comprises the steps of (a.)y flowing said milk in the form of a cascade through a plurality of freezing treatment stages and whereby the milk being concentrated passes from one freezing treatment stage to another down the series, (b) subjecting said milk in each stage to a freezing treatment and sufficient to cause the formation of ice crystals, (c) removing a portion of said iceA crystals and constituting the GEORGE L. CUNNINGHAM.

REFERENCES CITED The following Vreferences are of record in the le of this patent:

UNITED STATES PATENTS Name Number Date 523,677 McIntyre July 31, 1894 723,152 Gurber Mar. 17, 1903 994,555 Alexander June 6, 1911 1,576,137 Johnson Mar. 9Il 1926 

1. A METHOD OF TREATING LIQUID FOOD STUFFS TO PRODUCE A CONCENTRATE THEREOF WHICH COMPRISES THE STEPS OF (A) FLOWING SAID LIQUID FOOD STUFF IN THE FORM OF A CASCADE THROUGH A PLURALITY OF FREEZING TREATMENT STAGES AND WHEREBY THE LIQUID FOOD STUFF BEING CONCENTRATED PASSES FROM ONE FREEZING TREATMENT STAGE TO ANOTHER DOWN THE SERIES, (B) SUBJECTING SAID LIQUID FOOD STUFF IN EACH STAGE TO A FREEZING TREATMENT AND SUFFICIENT TO CAUSE THE FORMATION OF ICE CRYSTALS, (C) REMOVING A PORTION OF SAID ICE CRYSTALS FROM EACH TREATMENT STAGE AS THE LIQUID FOOD STUFF CASCADES DOWN THROUGH THE SERIES OF FREEZING TREATMENT STAGES, (D) TRANSFERRING THE ICE CRYSTALS REMOVED FROM ONE TREATMENT STAGE TO THE PRECEDING TREATMENT STAGE, AND (E) TREATING THE RESULTANT LIQUID FOOD STUFF AFTER PASSING THROUGH SAID CASCADE SERIES OF FREEZING TREATMENTS TO REMOVE THE REMAINING ICE CRYSTALS THEREFROM TO PRODUCE A CONCENTRATED LIQUID FOOD STUFF. 